kernel/git - git - PowerEL Git System

Author	SHA1	Message	Date
SZEDER Gábor	3cb9d2b6f9	line-log: more responsive, incremental 'git log -L' The current line-level log implementation performs a preprocessing step in prepare_revision_walk(), during which the line_log_filter() function filters and rewrites history to keep only commits modifying the given line range. This preprocessing affects both responsiveness and correctness: - Git doesn't produce any output during this preprocessing step. Checking whether a commit modified the given line range is somewhat expensive, so depending on the size of the given revision range this preprocessing can result in a significant delay before the first commit is shown. - Limiting the number of displayed commits (e.g. 'git log -3 -L...') doesn't limit the amount of work during preprocessing, because that limit is applied during history traversal. Alas, by that point this expensive preprocessing step has already churned through the whole revision range to find all commits modifying the revision range, even though only a few of them need to be shown. - It rewrites parents, with no way to turn it off. Without the user explicitly requesting parent rewriting any parent object ID shown should be that of the immediate parent, just like in case of a pathspec-limited history traversal without parent rewriting. However, after that preprocessing step rewrote history, the subsequent "regular" history traversal (i.e. get_revision() in a loop) only sees commits modifying the given line range. Consequently, it can only show the object ID of the last ancestor that modified the given line range (which might happen to be the immediate parent, but many-many times it isn't). This patch addresses both the correctness and, at least for the common case, the responsiveness issues by integrating line-level log filtering into the regular revision walking machinery: - Make process_ranges_arbitrary_commit(), the static function in 'line-log.c' deciding whether a commit modifies the given line range, public by removing the static keyword and adding the 'line_log_' prefix, so it can be called from other parts of the revision walking machinery. - If the user didn't explicitly ask for parent rewriting (which, I believe, is the most common case): - Call this now-public function during regular history traversal, namely from get_commit_action() to ignore any commits not modifying the given line range. Note that while this check is relatively expensive, it must be performed before other, much cheaper conditions, because the tracked line range must be adjusted even when the commit will end up being ignored by other conditions. - Skip the line_log_filter() call, i.e. the expensive preprocessing step, in prepare_revision_walk(), because, thanks to the above points, the revision walking machinery is now able to filter out commits not modifying the given line range while traversing history. This way the regular history traversal sees the unmodified history, and is therefore able to print the object ids of the immediate parents of the listed commits. The eliminated preprocessing step can greatly reduce the delay before the first commit is shown, see the numbers below. - However, if the user did explicitly ask for parent rewriting via '--parents' or a similar option, then stick with the current implementation for now, i.e. perform that expensive filtering and history rewriting in the preprocessing step just like we did before, leaving the initial delay as long as it was. I tried to integrate line-level log filtering with parent rewriting into the regular history traversal, but, unfortunately, several subtleties resisted... :) Maybe someday we'll figure out how to do that, but until then at least the simple and common (i.e. without parent rewriting) 'git log -L:func:file' commands can benefit from the reduced delay. This change makes the failing 'parent oids without parent rewriting' test in 't4211-line-log.sh' succeed. The reduced delay is most noticable when there's a commit modifying the line range near the tip of a large-ish revision range: # no parent rewriting requested, no commit-graph present $ time git --no-pager log -L:read_alternate_refs:sha1-file.c -1 v2.23.0 Before: real 0m9.570s user 0m9.494s sys 0m0.076s After: real 0m0.718s user 0m0.674s sys 0m0.044s A significant part of the remaining delay is spent reading and parsing commit objects in limit_list(). With the help of the commit-graph we can eliminate most of that reading and parsing overhead, so here are the timing results of the same command as above, but this time using the commit-graph: Before: real 0m8.874s user 0m8.816s sys 0m0.057s After: real 0m0.107s user 0m0.091s sys 0m0.013s The next patch will further reduce the remaining delay. To be clear: this patch doesn't actually optimize the line-level log, but merely moves most of the work from the preprocessing step to the history traversal, so the commits modifying the line range can be shown as soon as they are processed, and the traversal can be terminated as soon as the given number of commits are shown. Consequently, listing the full history of a line range, potentially all the way to the root commit, will take the same time as before (but at least the user might start reading the output earlier). Furthermore, if the most recent commit modifying the line range is far away from the starting revision, then that initial delay will still be significant. Additional testing by Derrick Stolee: In the Linux kernel repository, the MAINTAINERS file was changed ~3,500 times across the ~915,000 commits. In addition to that edit frequency, the file itself is quite large (~18,700 lines). This means that a significant portion of the computation is taken up by computing the patch-diff of the file. This patch improves the real time it takes to output the first result quite a bit: Command: git log -L 100,200:MAINTAINERS -n 1 >/dev/null Before: 3.88 s After: 0.71 s If we drop the "-n 1" in the command, then there is no change in end-to-end process time. This is because the command still needs to walk the entire commit history, which negates the point of this patch. This is expected. As a note for future reference, the ~4.3 seconds in the old code spends ~2.6 seconds computing the patch-diffs, and the rest of the time is spent walking commits and computing diffs for which paths changed at each commit. The changed-path Bloom filters could improve the end-to-end computation time (i.e. no "-n 1" in the command). Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
SZEDER Gábor	d5546726fb	line-log: remove unused fields from 'struct line_log_data' Remove the unused fields 'status', 'arg_alloc', 'arg_nr' and 'args' from 'struct line_log_data'. They were already part of the struct when it was introduced in commit `12da1d1f6` (Implement line-history search (git log -L), 2013-03-28), but as far as I can tell none of them have ever been actually used. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
Denton Liu	554544276a	.[ch]: remove extern from function declarations using spatch There has been a push to remove extern from function declarations. Remove some instances of "extern" for function declarations which are caught by Coccinelle. Note that Coccinelle has some difficulty with processing functions with `__attribute__` or varargs so some `extern` declarations are left behind to be dealt with in a future patch. This was the Coccinelle patch used: @@ type T; identifier f; @@ - extern T f(...); and it was run with: $ git ls-files \.{c,h} \| grep -v ^compat/ \| xargs spatch --sp-file contrib/coccinelle/noextern.cocci --in-place Files under `compat/` are intentionally excluded as some are directly copied from external sources and we should avoid churning them as much as possible. Signed-off-by: Denton Liu <liu.denton@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
Ramsay Jones	071bcaab64	ALLOC_GROW: avoid -Wsign-compare warnings Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	7 years ago
Junio C Hamano	2b102efc8c	line-log.c: make line_log_data_init() static No external callers exist. Signed-off-by: Junio C Hamano <gitster@pobox.com>	10 years ago
Eric Sunshine	c0babbe695	range-set: publish API for re-use by git-blame -L git-blame is slated to accept multiple -L ranges. git-log already accepts multiple -L's but its implementation of range-set, which organizes and normalizes -L ranges, is private. Publish the small subset of range-set API which is needed for git-blame multiple -L support. Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago
Thomas Rast	31c6191831	log -L: store the path instead of a diff_filespec line_log_data has held a diff_filespec* since the very early versions of the code. However, the only place in the code where we actually need the full filespec is parse_range_arg(); in all other cases, we are only interested in the path, so there is hardly a reason to store a filespec. Even worse, it causes a lot of redundant ->spec->path pointer dereferencing. And even worse, it caused the following bug. If you merge a rename with a modification to the old filename, like so: * Merge \| \ \| * Modify foo \| \| * \| Rename foo->bar \| / * Create foo we internally -- in process_ranges_merge_commit() -- scan all parents. We are mainly looking for one that doesn't have any modifications, so that we can assign all the blame to it and simplify away the merge. In doing so, we run the normal machinery on all parents in a loop. For each parent, we prepare a "working set" line_log_data by making a copy with line_log_data_copy(), which does not make a copy of the spec. Now suppose the rename is the first parent. The diff machinery tells us that the filepair is ('foo', 'bar'). We duly update the path we are interested in: rg->spec->path = xstrdup(pair->one->path); But that 'struct spec' is shared between the output line_log_data and the original input line_log_data. So we just wrecked the state of process_ranges_merge_commit(). When we get around to the second parent, the ranges tell us we are interested in a file 'foo' while the commits touch 'bar'. So most of this patch is just s/->spec->path/->path/ and associated management changes. This implicitly fixes the bug because we removed the shared parts between input and output of line_log_data_copy(); it is now safe to overwrite the path in the copy. There's one only somewhat related change: the comment in process_all_files() explains the reasoning behind using 'range' there. That bit of half-correct code had me sidetracked for a while. Signed-off-by: Thomas Rast <trast@inf.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago
Thomas Rast	12da1d1f6f	Implement line-history search (git log -L) This is a rewrite of much of Bo's work, mainly in an effort to split it into smaller, easier to understand routines. The algorithm is built around the struct range_set, which encodes a series of line ranges as intervals [a,b). This is used in two contexts: * A set of lines we are tracking (which will change as we dig through history). * To encode diffs, as pairs of ranges. The main routine is range_set_map_across_diff(). It processes the diff between a commit C and some parent P. It determines which diff hunks are relevant to the ranges tracked in C, and computes the new ranges for P. The algorithm is then simply to process history in topological order from newest to oldest, computing ranges and (partial) diffs. At branch points, we need to merge the ranges we are watching. We will find that many commits do not affect the chosen ranges, and mark them TREESAME (in addition to those already filtered by pathspec limiting). Another pass of history simplification then gets rid of such commits. This is wired as an extra filtering pass in the log machinery. This currently only reduces code duplication, but should allow for other simplifications and options to be used. Finally, we hook a diff printer into the output chain. Ideally we would wire directly into the diff logic, to optionally use features like word diff. However, that will require some major reworking of the diff chain, so we completely replace the output with our own diff for now. As this was a GSoC project, and has quite some history by now, many people have helped. In no particular order, thanks go to Jakub Narebski <jnareb@gmail.com> Jens Lehmann <Jens.Lehmann@web.de> Jonathan Nieder <jrnieder@gmail.com> Junio C Hamano <gitster@pobox.com> Ramsay Jones <ramsay@ramsay1.demon.co.uk> Will Palmer <wmpalmer@gmail.com> Apologies to everyone I forgot. Signed-off-by: Bo Yang <struggleyb.nku@gmail.com> Signed-off-by: Thomas Rast <trast@student.ethz.ch> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago